21,786 research outputs found
Lactobacillus fermentum NS9 restores the antibiotic induced physiological and psychological abnormalities in rats
Gut microbiota play a vital role in maintaining the health of the host. Many factors affect gut microbiota; application of broad range antibiotics disturb microbiota, while probiotic application protects the microbiota. To investigate how probiotics alter the physiological and psychological changes induced by antibiotics, we tested the performance of ampicillin-treated rats in the presence or absence of Lactobacillus fermentum strain NS9, in elevated plus maze and Morris water maze. The results showed that NS9 normalised the composition of gut microbiota and alleviated the ampicillin-induced inflammation in the colon. The levels of the mineralocorticoid and N-methyl-D-aspartate receptors were also elevated in the hippocampus of the ampillicin+ NS9 treated group. NS9 administration also reduced the anxiety-like behaviour and alleviated the ampicillin-induced impairment in memory retention. These findings suggest that NS9 is beneficial to the host, because it restores the physiological and psychological abnormalities induced by ampicillin. Our results highlight how gut contents regulate the brain, and shed light on the clinical applications of probiotics to treat the side effect of antibiotics and mental disorders
Observation of orbital ordering and origin of the nematic order in FeSe
To elucidate the origin of nematic order in FeSe, we performed
field-dependent 77Se-NMR measurements on single crystals of FeSe. We observed
orbital ordering from the splitting of the NMR spectra and Knight shift and a
suppression of it with magnetic field B0 up to 16 T applied parallel to the
Fe-planes. There is a significant change in the distribution and magnitude of
the internal magnetic field across the orbital ordering temperature Torb while
stripe-type antiferromagnetism is absent. Giant antiferromagnetic (AFM) spin
fluctuations measured by the NMR spin-lattice relaxation are gradually
developed starting at ~ 40 K, which is far below the nematic ordering
temperature Tnem. These results demonstrate that orbital ordering is the origin
of the nematic order, and the AFM spin fluctuation is the driving mechanism of
superconductivity in FeSe under the presence of the nematic order.Comment: 6 pages, 4 figure
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Evaluating the lingering effect of livestock grazing on functional potentials of microbial communities in Tibetan grassland soils
Background and aims: Livestock grazing is a widely practiced land-use regime that can impose lingering effects on global biogeochemical cycles. However, elucidating the mechanisms of related eco-processes, which are largely mediated by the microbial community, remains challenging. Methods: Here, we collected soil samples from two Tibetan grassland sites subjected to grazing in winter followed by a 3-month recovery. We then evaluated functional potentials of microbial communities via a metagenomic tool known as GeoChip 4.0. Results: Significant alterations were detected in post-grazing grassland soils, and further analysis showed that plant diversity was the best indicator of alterations in functional potentials. Relative abundances of labile C degradation genes decreased at the 3400-m site, but those of recalcitrant C degradation genes increased, which could be explained by the higher soil recalcitrant C input owing to their being substantially more forbs species at this site. Nitrification genes decreased at both sites, probably owing to increased soil moisture conducive to oxygen-limiting conditions. Relative abundance of denitrification genes increased at the 3200-m site, concomitant with increased N2O emissions. Conclusions: These results demonstrated that functional gene compositions of the microbial community were altered in post-grazing grassland soils, and linked to soil biogeochemical processes
Flat optical conductivity in topological kagome magnet TbMnSn
Kagome magnet TbMnSn is a new type of topological material that is
known to support exotic quantum magnetic states. Experimental work has
identified that TbMnSn hosts Dirac electronic states that could lead to
topological and Chern quantum phases, but the optical response of the Dirac
fermions of TbMnSn and its properties remain to be explored. Here, we
perform optical spectroscopy measurement combined with first-principles
calculations on single-crystal sample of TbMnSn to investigate the
associated exotic phenomena. TbMnSn exhibits a frequency-independent
optical conductivity spectra in a broad range from 1800 to 3000 cm
(220-370 meV) in experiments. The theoretical band structures and optical
conductivity spectra are calculated with several shifted Fermi energy to
compare with the experiment. The theoretical spectra with 0.56 eV shift for
Fermi energy are well consistent with our experimental results. Besides, the
massive quasi-two-dimensional (quasi-2D) Dirac bands, which have linear band
dispersion in - plane and no band dispersion along the
direction, exist close to the shifted Fermi energy. According to tight-bond
model analysis, we find that quasi-2D Dirac bands give rise to a flat optical
conductivity, while its value is smaller than the result by calculations and
experiments. It indicates that the other trivial bands also contribute to the
flat optical conductivity
Direct measurement of photoinduced transient conducting state in multilayer 2H-MoTe2
Ultrafast light-matter interaction has emerged as a powerful tool to control
and probe the macroscopic properties of functional materials, especially
two-dimensional transition metal dichalcogenides which can form different
structural phases with distinct physical properties. However, it is often
difficult to accurately determine the transient optical constants. In this
work, we developed a near-infrared pump - terahertz to midinfrared (12-22 THz)
probe system in transmission geometry to measure the transient optical
conductivity in 2H-MoTe2 layered material. By performing separate measurements
on bulk and thin-film samples, we are able to overcome issues related to
nonuniform substrate thickness and penetration depth mismatch and to extract
the transient optical constants reliably. Our results show that photoexcitation
at 690 nm induces a transient insulator-metal transition, while photoexcitation
at 2 um has a much smaller effect due to the photon energy being smaller than
the band gap of the material. Combining this with a single-color pump-probe
measurement, we show that the transient response evolves towards 1T' phase at
higher flunece. Our work provides a comprehensive understanding of the
photoinduced phase transition in the 2H-MoTe2 system.Comment: Phys.Rev.Applied accepted, 9 pages, 11 figure
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